Garmin Striker 4DV RUGGED DESIGN - New rugged, outdoor look complements your lifestyle. Able to withstand the harsh marine environment with excellent performance. HIGH-SENSITIVITY GPS - The built-in GPS receiver allows you to mark your favorite fishing spot and get back to it tomorrow. This also allows the device to display GPS speed so you know how fast you are trolling. WAYPOINT MAP - Use the waypoint map to easily view, mark and navigate to locations such as brush piles, stumps and docks. CHIRP SONAR - CHIRP sends a continuous sweep of frequencies ranging from low to high which provides a wider range of information. CHIRP sonar is able to create crisper fish arches with greater target separation. BUILT-IN FLASHER - View your sonar data in the classic flasher format; ideal for ice fishing or vertical jigging.